This invention relates to an improved transportation and/or storage container for radioactive substances, especially for irradiated fuel elements from nuclear reactors.
Containers which are used for the transportation and/or storage of spent nuclear fuel elements must safely enclose the radioactivity of such elements and ensure such safe enclosure even in the event of an extreme accident. Such containers not only must shield or prevent exterior emissions of the gamma- and n-radiation being given off by radioactive decomposition reactions of such elements but also must transfer safely to the outside the heat generated by such reactions.
Known containers, as disclosed for example by the German Pat. OS No. 22 28 026, have open-top thick-walled metallic container bodies closed by a thick metallic removable cover to ensure the necessary strength and shielding against gamma rays. The bodies are provided with exterior cooling ribs or fins and shielding against neutrons. They also are provided with an interior lining for protection against corrosion and to facilitate decontamination. For reasons of handling, testing and storing, the interior linings preferably ae constructed as removable inside containers or enclosures.
These prior containers have a number of disadvantages. The interior lining is fastened in the container body either by clamping elements holding it down or else attached by screws in the area of the container cover, both of which expedients are expensive. Thus, for example in the case of attachment with screws, two rows of tapped holes are necessary; one row to fasten the inside lining firmly to the body and the other row to fasten the cover to the container body. Besides this expensive fastening arrangement, a further disadvantage is that the inside lining is perforated by holes for the screws, and thus the container body is exposed to attack by corrosion. Also, the space requirements for such a screw attchement system are undesirably large.
An additional disadvantage of know containers is the fact that the gap or interspace between the container body and the inside lining cannot be monitored, which limits the use of such containers for storage purposes because of the lack of or the possibility of only incomplete integrity tests during the storage time which often lasts several years.
Furthermore, in hitherto known containers having welded-on or cast-on cooling ribs, there exists the danger in the case of an accident, for example, a container is dropped and cracks or breaks off one or more cooling ribs, that a crack may continue into the container body, representing the tight enclosure of the radioactive substances.